1. Field of the Invention
The present invention generally relates to a private branch exchange (PBX) network system, and more particularly to a private branch exchange network system including a plurality of private branch exchanges connected to an integrated services digital network (ISDN).
2. Description of the Related Art
FIG. 1 is a diagram showing a PBX network having PBXs 10 and 12 connected to an ISDN 14. The PBXs 10 and 12 are local switch devices. An ISDN tie line 16 connects the PBXs 10 and 12 together. Terminals such as telephone sets are connected to the PBXs 10 and 12 so that a PBX network is formed. For the sake of simplicity, only one telephone set 18 connected to the PBX 10 is illustrated, and only one telephone set 20 connected to the PBX 12 is illustrated. The telephone sets 18 and 20 are respectively connected to extensions of the PBXs 10 and 12, and will be referred to as extension telephone sets hereinafter.
The PBX 10 sends a message to the PBX 12 over the ISDN tie line 16, and PBX 12 sends a message to the PBX 10 thereover. For example, the message sent by the PBX 10 includes the identification number of the PBX 10, and a ID of the calling terminal, that is, the extension telephone set 18. In FIG. 1, the PBXs 10 and 12 are respectively assigned identification numbers xe2x80x9c700xe2x80x9d and xe2x80x9c710xe2x80x9d, and the extension telephone sets 18 and 20 are respectively assigned IDs xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d.
Telephone sets 22 and 24 are connected to the ISDN 14, and are assigned IDs xe2x80x9cXxe2x80x9d and xe2x80x9cYxe2x80x9d, respectively. The telephone set 22 can call the extension telephone set 20 via the ISDN 14, the PBX 10, the ISDN tie line 16 and the PBX 12. However, in this case, the message sent to the PBX 12 from the PBX 10 includes the identification number xe2x80x9c700xe2x80x9d of the PBX 10 and the identification number of the ISDN network, but does not include the ID xe2x80x9cXxe2x80x9d of the calling telephone set 22. Hence, the called telephone set 20 is not informed of the ID xe2x80x9cXxe2x80x9d of the calling telephone set 22. This is inconvenient when the extension telephone set 20 calls the telephone set 22 by return.
The extension telephone set 18 can call the telephone set 24 via the ISDN tie line 16, the PBX 12, the ISDN 14. In this case, the message sent to the PBX 12 from the PBX 10 includes the identification number xe2x80x9c700xe2x80x9d of the PBX 10 and the ID xe2x80x9cAxe2x80x9d of the calling telephone set 18. However, the message sent to the telephone set 24 from the ISDN 14 does not include the ID xe2x80x9cAxe2x80x9d of the calling telephone set 18. This is inconvenient when the telephone set 24 calls the extension telephone set 18 connected to the PBX 10 by return.
It is a general object of the present invention to provide a switch device and a system in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide a switch device and a system capable of informing a called terminal of information indicative of the identification of the calling terminal, which may be accommodated by a local switch (PBX) or an ISDN, so that the identification information of the calling terminal can be displayed or the called terminal can easily call the calling terminal by return.
These objects of the present invention are achieved by a switch device connectable to an ISDN, the switch device comprising: a first part which adds a calling ID information element to a first call setup message to be transferred over an ISDN tie line connecting the switch device to another switch device, the calling ID information element including identification information on a terminal which is connected to the ISDN and makes a call.
The switch device may further comprise a second part which receives the first call setup message transferred via the ISDN tie line from another switch device and writes the calling ID information element into a second call setup message to be transferred over the ISDN so that the switch device calls the terminal connected to the ISDN.
The switch device may further comprise a third part which allows a first extension terminal connected to the switch device to communicate with the terminal connected to the ISDN upon receiving a call therefrom and then calls a second extension terminal connected to another switch device or another terminal connected to the ISDN via the ISDN tie line.
The above objects of the present invention are also achieved by a switch device connectable to an ISDN, the switch device comprising: a first part which translates an extension number of an extension terminal connected to the switch device into a dial-in number; and a second part which adds the dial-in number to a first call setup message to be transferred over an ISDN tie line connecting the switch device to another switch device.
The switch device may further comprise a third part which receives the first call setup message transferred via the ISDN tie line from another switch device and writes the dial-in number into a second call setup message to be transferred over the ISDN so that the switch device calls the terminal connected to the ISDN.
The switch device may further comprise a fourth part which allows a first extension terminal connected to the switch device to communicate with the terminal connected to the ISDN upon receiving a call therefrom and then calls a second extension terminal connected to another switch device or another terminal connected to the ISDN via the ISDN tie line.
The above objects of the present invention are also achieved a system comprising: a first device and a second device which are connected to an ISDN, the first switch device comprising: a first part which adds a calling ID information element to a first call setup message to be transferred over an ISDN tie line connecting the first and second switch devices together, the calling ID information element including identification information on a terminal which is connected to the ISDN and makes a call.
The system may be configured so that the second switch device comprises a second part which receives the first call setup message transferred from the first switch device via the ISDN tie line and writes the calling ID information element into a second call setup message to be transferred over the ISDN so that the second switch device calls the terminal connected to the ISDN.
The system may be configured so that the first switch device comprises a third part which allows a first extension terminal connected to the first switch device to communicate with the terminal connected to the ISDN upon receiving a call therefrom and then calls a second extension terminal connected to the second switch device or another terminal connected to the ISDN via the ISDN tie line.
The system may be configured so that the first switch device comprises a third part which allows a first extension terminal connected to the first switch device to communicate with the terminal connected to the ISDN upon receiving a call therefrom and then calls a second extension terminal connected to the second switch device or another terminal connected to the ISDN via the ISDN tie line.
The above objects of the present invention are also achieved by a system comprising: a first switch and a second switch connected to an ISDN, the first switch device comprising: a first part which translates an extension number of an extension terminal connected to the first switch into a dial-in number; and a second part which adds the dial-in number to a first call setup message to be transferred to the second switch over an ISDN tie line connecting the first and second switch devices together.
The system may be configured so that the first switch device comprises a third part which receives the first call setup message transferred over the ISDN tie line from the first switch device and writes the dial-in number into a second call setup message to be transferred over the ISDN so that the second switch device calls the terminal connected to the ISDN.
The system may be configured so that the first switch device comprises a fourth part which allows a first extension terminal connected to the first switch device to communicate with the first terminal connected to the ISDN upon receiving a call therefrom and then calls a second extension terminal connected to the second switch device or another terminal connected to the ISDN via the ISDN tie line.